Remote code execution in PyYAML parser and emitter for Python

1) Input validation error

EUVDB-ID: #VU25823

Risk: High

CVSSv4.0: 8.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2020-1747

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to insufficient validation of user-supplied input when processing untrusted YAML files passed via the "full_load" method or with the "FullLoader" loader. A remote attacker can pass specially crafted input to the application and execute arbitrary code by abusing the python/object/new constructor.

Mitigation

Install update from vendor's website.

Vulnerable software versions

PyYAML: 3.01 - 5.3

CPE2.3

• cpe:2.3:a:the_yaml_project:pyyaml:3.01:*:*:*:*:python:*:*
• cpe:2.3:a:the_yaml_project:pyyaml:3.02:*:*:*:*:python:*:*
• cpe:2.3:a:the_yaml_project:pyyaml:3.03:*:*:*:*:python:*:*

External links

https://snyk.io/vuln/SNYK-PYTHON-PYYAML-559098
https://github.com/yaml/pyyaml/pull/386
https://bugzilla.redhat.com/show_bug.cgi?id=1807367

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.